In a telephone network, a telephone loop is the wired connection from a telephone company's central office in a city to the residences and businesses of the customers. The central office includes switching equipment that switches telephone calls locally or to long-distance carrier telephone offices. Typically each city has its own telephone central office and each central office includes one or more wire centers where the number of wire centers depends on the number of customers or subscribers in the city. The telephone loop consists of one or more segments of twisted pair copper wires spliced together and was originally designed for voice transmissions on a single voice channel.
DSL Internet services allow residential and business customers to receive broadband Internet services over the telephone loop of the telephone network. But in order to receive DSL services, the residences and businesses must be within a certain distance of the telephone company's central office, and the twisted pair of copper wire must be of a particular gauge. Therefore the telephone companies must keep accurate records regarding wire gauge and the distances from the central office to residences and businesses, so that when a customer requests DSL service, the telephone company will be able to quickly determine if the customer is within the required distance and therefore eligible to receive DSL service.